Many researches have been made on various derivatives of kanamycin A and kanamycin B, but the kanamycin derivatives which were synthetized in the past are limited almost to those obtained by modification of the 3'-hydroxyl group, 4'-hydroxyl group, 1-amino group and/or 6'-amino group of kanamycins, as disclosed e.g. in Japanese patent publication No. 7595/75 or the corresponding U.S. Pat. No. 3,753,973; Japanese patent application pre-publication "Kokai" No. 80038/74; U.S. Pat. No. 3,929,761; U.S. Pat. No. 3,929,762; Japanese patent publication No. 12039/80; U.S. Pat. No. 3,948,882; U.S. Pat. No. 3,939,143; U.S. Pat. No. 4,170,642 and other. This is mainly because the previous researches were made on the basis of the findings that resistant strains of bacteria have their mechanism of resistance against the aminoglycosidic antibiotics owing to their production of the various inactivating enzymes which would attack the 3'-hydroxyl group, 4'-hydroxyl group, 3-amino group, 2"-hydroxyl group and/or 6'-amino group of the aminoglycosidic antibiotics. The previous researches have succeeded to provide different derivatives of the kanamycins which are actually useful in therapeutic treatment of bacterial infections. The problem of semi-synthetizing the 2'-modified derivatives of kanamycins has been discussed and studied in recent years, but it has been found that chemical modification is difficult to be effected preferentially at the 2'-position of kanamycins. Accordingly, the intended 2'-modified derivatives of kanamycins actually have never been obtained.
We, the present inventors, attempted to effect the chemical modification at the 2'-position of kanamycins. As a result of our continued researches, we have now succeeded to achieve the preferential, chemical modification of the 2'-position of kanamycins and actually to synthetize 2'-deoxykanamycin A, 2'-epikanamycin A and 2'-epikanamycin B as the new compounds. These 2'-modified kanamycin derivatives are found to exhibit a high antibacterial activity, so that they are useful in therapeutic treatment of various bacterial infections by gram-positive bacteria and by gram-negative bacteria.